stokes.] TRI- AND TETRAPHOSPHONITRILIC CHLORIDES. 79 
have proposed 1 to reserve the name amido-orthophosphorie acid for the 
ortho acid in which one hydroxyl is replaced by the araido group, and 
to call the isomeric form P(NH)(OH) ;i orthophosphimic acid. By anal- 
ogy an acid P(NH) X qjj might be named metaphosphimic acid. Cor- 
responding to the polymeric metaphosphoric acids we may imagine an 
homologous series of metaphosphimic acids, but for each of these sev- 
eral forms would be possible, according as the polymerization is effected 
by means of oxygen or of nitrogen atoms, assuming them to be other- 
wise built on the same general type. For example, an acid of the for- 
mula P2N2O4H4, with cyclic structure, might have any of the following 
constitutional formulas, omitting mixed forms: 
PO.NH, P(NH).OH PO.OH P(OH), 
0\/0 °\/° NH^NH N \/ N 
PO.NH 2 P(NH).OH PO.OH P(OH), 
(a) (6) (c) (d) 
Dimetaphosphoryl Dimetaphosphimic Diphosphonitrilic 
a mide. acid. acid. 
(a) and (b) represent the amide of a dimetaphosphoric acid with its 
desmotropic form; (c) and (d) represent the two forms of an acid isomeric 
with the former, but not directly derivable from a dimetaphosphoric 
acid. In the former class, phosphorus is united by means of oxygen; 
in the latter, by nitrogen, (b) and (c) are polymers of (PO) (NH) (OH) 
while (d) is a polymer of an acid N ~ P(OH) 2 , which we may call phos- 
phouitrilic acid. Acids of the type (c) I call a?- metaphosphimic acids, 
and those of the type (d) y #-phosphonitrilic acids. 2 
In the chlorides P 3 N 3 G1 6 and P 4 K 4 01 8 , phosphorus must be united by 
means of nitrogen 3 (in the absence of oxygen); hence also in all prob- 
ability in the acids derived from them. The direct replacement of 
chlorine by hydroxyl would result in phosphonitrilic acids, but as the 
type (c) is equally plausible, in the absence of definite experimental 
grounds, I call them, provisionally, metaphosphimic acids. For the 
chlorides themselves, instead of the old term chlorophosphuret of 
nitrogen, which is no longer characteristic, the more definite names 
tri- and tetraphosphonitrilic chloride may be used. 
Experimental Part. 
Preparation of the chlorides. — The theoretical yield of triphospho- 
nitrilic chloride is 55.5 per cent of the phosphorus pentachloride; in 
reality, it falls far below this, no matter what process may be employed, 
and at best is but a by-product. Gladstone 4 states the yield as 
1 Am. Chem. Jour., Vol. XVI, p. 124, note. 
2 la; — mono-, di-, tri-, etc. 
3 Unless we assume P to be joined to P, and N to N, a view which is not supported by tin'ir general 
behavior. 
4 Quart. Jour. Chem. Soc. London, Vol. Ill, p. 135 ; Ann. Chem. (Liebig), Vol. LXXVI, p. 76. 
